BacteriaCharacteristics of Bacteria | Reproduction of

Bacteria

• Single-celled prokaryotic organisms

• Contain cell walls composed of a protein and carbohydrate matrix called peptidoglycan– Structurally different from Archaea or plants

• Do not contain a nucleus or membrane-bound organelles

Characteristics of Bacteria

• Nucleoid – region within bacteria where DNA is organized

• Plasmids are small circular segments of bacterial DNA

• All contain: – Plasma membrane– Cytoplasm– Ribosomes – Capsule – a protective coating outside of bacterial

cell walls

• Some contain:– Flagella which are used for locomotion– Pili function in some forms of reproduction

Characteristics of Bacteria

Characteristics of Bacteria

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Streptococcus Causes Strep Throat

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Bacillus - E. coli

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Spirochetes

• Bacteria are very diverse– Some are autotrophs– Some perform photosynthesis with chlorophyll– Some perform chemosynthesis

• Deep sea vents, other ocean environments, and hot springs

• Some are heterotrophic– Obtain energy by absorbing or ingesting food

Characteristics of Bacteria

• Aerobic bacteria – require oxygen in the process of cellular respiration

• Anaerobic bacteria – do not use oxygen

Characteristics of Bacteria

• Cell division = reproduction in prokaryotes

• Binary fission – simplified form of cell division used by bacteria

• Steps:– DNA is replicated – Cell increases in size, splits in two – Plasma membrane pinches together and a new

cell plate forms – Control of the bacterial cell cycle: growth rates,

biochemical signals, and environmental conditions

Reproduction of Bacteria

Reproduction in Bacteria

• Ability to exchange DNA with another bacterium

• Conjugation – exchange of DNA in bacteria– Similar to genetic recombination in eukaryotes

Reproduction in Bacteria

• Donor bacterium connects to another bacterium using pilus

• DNA is transferred to the recipient cell through pilus– Aided by proteins

• DNA donated can be a plasmid

• Donated DNA may contain beneficial genes

Reproduction in Bacteria

• Some bacteria disrupt the health of other organisms

• Pathogenic – bacteria that cause disease

• Bacterial diseases are spread through: – Droplets in the air– Direct contact with the bacterium – On surfaces– In fluids– Through contaminated food

Diseases Caused by Bacteria

• Streptococcal disease – any bacterial disease, including strep throat, that is caused by streptococcus genus

• Common infection in children• Highly contagious• Symptoms: – Sudden fever– Aches– Nausea– Red throat with possible white patches

• Treated with antibiotics

Diseases Caused by Bacteria

• Impact of bacteria on biosphereProduce oxygen

– Bacteria decompose dead plant and animal matter• Release carbon dioxide into atmosphere

• Multicellular organisms have bacteria living in their digestive tract– Mutualistic relationship– Bacteria break down indigestible compounds for

host to absorb– Bacteria receive nutrition and a place to live

Ecological Impact of Bacteria

• Bacteria maintain health of organisms through biotechnology

– Vaccines and antibiotics

• Bacteria used in genetic engineering

Ecological Impact of Bacteria

• Bacteria help in producing and cycling nitrogen– Bacteria in soil make nitrogen useable through

nitrogen fixation– Break down dead organisms and waste into

ammonium– Other bacteria then change ammonium into

nitrates for plants

• These bacterial processes allow nitrogen to cycle– From atmosphere– Through food chain– Within soil

Ecological Impact of Bacteria

Nitrogen Cycle